The present invention relates to the field of endovascular grafts for use in repairing aneurysms.
Various fluid-conducting body lumens, such as veins, arteries, and ducts such as the bile duct, may deteriorate or suffer trauma so that repair is necessary. For example, various types of aneurysms or other deteriorative diseases may affect the ability of the lumen to conduct fluids and, in turn, may be life threatening. An aneurysm is a sac resulting from abnormal dilation of the artery wall. Unless treated, an aneurysm can rupture, leading to severe and often fatal hemorrhaging. Treating an aneurysm, for example an aortic aneurysm, generally involve implanting a prosthetic graft to bridge the affected section of the aorta. Surgical techniques known in the art involve major surgery in which a graft resembling the natural vessel, such as a donor graft or an artificial graft, is inserted into the diseased section of the natural vessel. Surgical implantation, however, causes considerable trauma, results in high mortality and morbidity and, even when completely successful, requires a lengthy recuperation period.
Medical improvements now also allow graft implantation to be done less invasively. In particular, endovascular surgery permits intraluminal repair using a catheter delivery system, without necessity for invasive surgery. The graft is packed into the delivery system and passed through the body lumen, for example through the femoral artery, to be implanted at the desired location. Generally speaking, intraluminal repair, where it is a viable alternative, can be performed more safely and with less trauma to the patient. Moreover, since intraluminal repair does not require major surgery, the recovery time from such a procedure is usually shorter.
Textile vascular grafts are widely used as prostheses to replace or repair damaged or diseased body lumens. Such grafts are generally formed by knitting, weaving or braiding suitable yarn. The endovascular prosthetic textile must be made very thin to permit introduction into the vessel via a catheter delivery system passed through the patient""s vasculature. In addition, the graft must have high structural integrity to withstand pressures exerted on the graft by the fluid contained in the lumen and pressures exerted by subsequent balloon expansion on the catheter during implantation.
Treatment of an abdominal aortic aneurysm (AAA) commonly involves placement of a unibody bifurcated vascular graft having a tubular trunk section and a pair of tubular limb sections extending from the trunk section. When implanted endovascularly, the trunk section is secured within the abdominal aortic artery, while each of the limbs extends downwardly into one of the iliac arteries. Grafts available for this purpose fall into two general categories: unibody grafts and modular grafts. Unibody grafts are provided with the trunk and limb sections forming a single piece of textile with both limbs having sufficient length to reach the iliac arteries, respectively. Unibody grafts are implanted whole into the arterial system using a catheter delivery system, and manipulated to situate the trunk and limbs into their appropriate positions.
Modular grafts are provided in two or more separate sections. For example, one section may comprise the trunk, one of the limbs, and a stump limb that is not of sufficient length to extend into an iliac artery. The other section comprises the second limb to be mated with the stump limb to provide the length needed to extend into an iliac artery. The components are separately introduced into the patient""s vasculature, typically with one section being introduced contralaterally and the other being introduced ipsilaterally. The sections are held together by friction or engagement after they have been separately introduced into the patient""s vasculature.
Before s/he implants a vascular graft for AAA repair, the surgeon measures the respective diameters of the healthy portion of the abdominal aortic artery just below the renal arteries, and each of the iliac arteries. S/he then selects a graft of appropriate size for implantation. The unibody and modular grafts are typically provided in a variety of dimensions so as to accommodate a wide range of vessel sizes. The proportions of unibody grafts typically follow a standard formula in which the trunk has a first inner diameter and in which the limbs are equal in inner diameter to one another. The inner diameter of each limb is one-half the inner diameter of the trunk. In other words, a 26 mm graft would have a trunk diameter of 26 mm, and two limbs each 13 mm in diameter. This standard proportion for unibody grafts is due to manufacturing considerations. The grafts are generally formed by knitting, weaving or braiding suitable yarn.
Because modular grafts are provided in multiple pieces, a surgeon may elect to implant limbs of unequal diameters if the patient""s vessel diameters warrant doing so. In this regard, modular grafts are beneficial in that they provide the surgeon with a greater number of size options for each patient. However, modular grafts suffer from potential drawbacks in that the pieces of the graft may leak at their junction or become disconnected after they have been introduced into the patient""s vasculature. Disconnects can lead to undesirable leaks or ruptures in the graft or vessel.
It is highly desirable to increase the population of patients eligible for intraluminal AAA repair in order to minimize the number of patients who must undergo the more complicated open surgical procedure. It is thus desirable to provide a unibody vascular graft which is not limited by the standard formula for graft dimensions and that thus provides the surgeon with numerous size options for each patient, and that also does not have the risk of disconnecting or leaking,.
To provide consistency with the common usage of terms used in the medical surgical arts in the United States, the terms xe2x80x9cinferior and superiorxe2x80x9dare used with a certain regularity within the present specification. Superior refers to a location situated above and is used herein in the description of the graft and attachment system. Inferior refers to the point situated below and again is used herein with the graft and attachment system. Thus, for applications in the abdominal aorta which use a femoral approach, the superior end of the graft resides within the aorta. Likewise, the inferior ends of the graft reside within the iliac arteries.
The term xe2x80x9cipsilateralxe2x80x9d typically refers to a vessel or part of a device which resides on the same side in which a device enters a lumen. For example, the ipsilateral tubular leg of a graft would be the tubular leg which resides in the iliac artery in which the delivery catheter enters the aorta. Similarly, the term xe2x80x9ccontralateralxe2x80x9d refers to a vessel or device residing on the opposite side of which the catheter enters the aorta. For example, the contralateral attachment system resides in the contralateral iliac artery which is on the opposite side of the aorta from which the delivery catheter enters the aorta.
The present invention is a unibody or modular bifurcated vascular graft having a tubular trunk with an inner diameter. Tubular limbs having respective inner diameters extend longitudinally from the trunk, and the diameter of at least one of the limbs is unequal to half the trunk diameter. In one embodiment, the graft is flared such that the combined diameters of the limbs exceed the diameter of the trunk. In another embodiment, the graft is tapered such that the diameter of the trunk exceeds the combined diameters of the limbs. In a third embodiment, the limb diameters are unequal to one another. Additional embodiments utilize tapers and/or flares having various positions relative to the superior and inferior regions of the graft.